In oilfield terminology, a gas-oil separator designates a pressure vessel used for separating well fluids produced from oil and gas wells into gaseous and liquid components. In petroleum production, for example, a gas-oil separator (or simply separator) is a vessel designed to separate production fluids into their constituent components of oil, gas and water. A separating vessel may be referred to in a variety of ways, such as stage separator, flash chamber, etc. Commonly, gas-oil separators are installed as part of the surface facilities. Thus, gas-oil separation typically takes place after the production fluid reaches the surface and leaves the production well.
One apparatus used in oil and associated gas production is a positive displacement pump. Associated gas is a form of natural gas which is found with deposits of petroleum, either dissolved in the oil or as a free gas cap above the oil in the reservoir. A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into a discharge channel. Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses.
A progressive cavity pump is a type of positive displacement pump and is also known as a progressing cavity pump. It transfers fluid by means of the progress, through the pump, of a sequence of discrete cavities, as its rotor is turned. This leads to the volumetric flow rate being proportional to the rotation rate and to low levels of shearing being applied to the pumped fluid. The cavities taper down toward their ends and overlap with adjacent cavities.
Maximum efficiency of the progressing cavity pump occurs when oil is pumped without the presence of associated gas. One of the problems causing pumping efficiency loss in progressive cavity pumps involves the entrance of excess associated gas into the pumping device. In production wells where there is a gas-to-oil ratio above 20 standard cubic feet of gas per standard barrel of oil (GOR), the pumping efficiency of the progressive cavity pump is lowered significantly, thus rendering a low oil production rate.
Therefore, a need exists for improvements over the prior art, and more particularly for methods and systems that increase the pumping efficiency of positive displacement pumps.